Chapter 2: The Chemistry of Life (Biochemistry)

Vocabulary flashcards covering key concepts from Chapter 2 notes on biochemistry and the chemistry of life.

Atom

The smallest unit of matter; the basic unit of an element; the word atom comes from Greek for indivisible.

Bohr model

Planetary model of atomic structure with a nucleus and electrons in shells; electrons are negative, protons positive, neutrons neutral.

Nucleus

Center of the atom where protons and neutrons are bunched together.

Proton

Positively charged subatomic particle inside the nucleus; has 1 atomic mass unit (amu).

Neutron

Electrically neutral subatomic particle inside the nucleus; has 1 amu.

Electron

Negatively charged subatomic particle that orbits the nucleus in electron shells; very small mass.

Atomic number

Number of protons in the nucleus; identifies the element and is always a whole number.

Atomic mass

Total number of protons and neutrons in the nucleus (mass number).

Isotopes

Variants of an element that differ in the number of neutrons but have the same number of protons; atomic mass varies.

Atomic weight

Weighted average of the isotopes of an element.

Ion

A charged particle with an unequal number of protons and electrons.

Anion

Negatively charged ion.

Cation

Positively charged ion.

Electrolyte

Salts that ionize in water and conduct electricity; essential for osmotic balance and nerve/muscle impulses.

Free radical

Unstable, highly reactive atoms or molecules with an unusual number of electrons; can damage molecules.

Antioxidant

Substances that neutralize free radicals.

Ionic bond

Electrical attraction between oppositely charged ions (cations and anions).

Covalent bond

Atoms share one or more pairs of electrons.

Hydrogen bond

Weak attraction between a slightly positive hydrogen atom and a slightly negative atom (O or N) in another molecule; important in water and biomolecules.

Molecule

Two or more atoms bonded together.

Compound

A molecule composed of two or more different elements.

Isomer

Molecules with identical molecular formulas but different arrangements of atoms.

Water

Universal solvent; polar covalent bonds; forms hydration spheres; essential for solvency and many metabolic reactions.

Hydrophilic

Water-loving; dissolves in water; polar or charged substances.

Hydrophobic

Water-fearing; nonpolar substances that do not dissolve in water.

pH

Measure of hydrogen ion concentration; acids donate H+, bases accept H+ and release OH-; scale from 0 to 14.

Acid

Proton donor; releases hydrogen ions into water; lower pH.

Base

Proton acceptor; releases hydroxide ions into water; higher pH.

Buffer

Chemical solution that resists changes in pH.

Carbohydrates

Carbon, hydrogen, and oxygen molecules; hydrophilic; include monosaccharides, disaccharides, and polysaccharides.

Monosaccharides

Single sugar units (e.g., glucose, galactose, fructose).

Glucose

A monosaccharide; primary fuel for ATP production in cells.

Disaccharides

Two monosaccharides linked together (e.g., sucrose, lactose, maltose).

Sucrose

Disaccharide consisting of glucose and fructose.

Polysaccharides

Many monosaccharides linked together (e.g., glycogen, starch, cellulose).

Lipids

Fats and related molecules; energy storage; include phospholipids, triglycerides, steroids.

Phospholipids

Lipids with two fatty acid tails and a phosphate-containing head; amphipathic; form cellular membranes.

Cholesterol

Steroid lipid; important for membrane structure and as a precursor to other steroids; largely synthesized in the liver.

Protein

Polymer of amino acids; performs structural, enzymatic, signaling, transport, and other functions.

Amino acid

Building block of proteins; 20 types distinguished by their R group.

Peptide bond

Bond joining amino acids via dehydration synthesis.

Enzyme

Biological catalyst; typically a protein that speeds up biochemical reactions.

Active site

Pocket or region of an enzyme where the substrate binds.

Cofactor

Non-protein helper for enzymes; inorganic cofactors (e.g., Fe, Cu, Zn, Mg, Ca) or organic cofactors (coenzymes).

Coenzyme

Organic cofactors derived from vitamins (e.g., NAD+ from niacin) that participate in enzyme reactions.

ATP

Adenosine triphosphate; the body’s main energy transfer molecule; energy stored in phosphate bonds and released for work.

Glycolysis

First stage of glucose metabolism; splits glucose into two pyruvate; produces about 2 ATP; occurs in the cytoplasm.

Pyruvate

End product of glycolysis; can enter aerobic respiration in mitochondria or be reduced to lactate in anaerobic conditions.

Aerobic respiration

Requires oxygen; yields about 30–34 ATP per glucose via mitochondrial pathways.

Anaerobic respiration

Occurs without oxygen; produces lactate (in muscles) and far less ATP.

DNA

Deoxyribonucleic acid; stores genetic information in genes; made of nucleotides.

RNA

Ribonucleic acid; carries out genetic instructions and helps assemble proteins; made of nucleotides.

Nucleotide

Monomer of nucleic acids; consists of a sugar, phosphate, and a nitrogenous base.